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Global constraint
Posted Jan 3, 2011, 5:16 p.m. EST Version 4.0a 1 Reply
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Hi,
Would you please help me out? I’m working with COMSOL v4a. I want to define a global constraint for electric field norm (ec.norm) using point integration and Global equation under ge model with non-zero initial condition. But I have this error:
Attempt to evaluate negative power of zero.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.ec.normE@VDN$mod1.Vy
- Defined as: (((-conj(mod1.ec.Ey))+(-conj(mod1.ec.Ey)))*((((realdot(mod1.ec.Ex,mod1.ec.Ex)+realdot(mod1.ec.Ey,mod1.ec.Ey))+realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5)*0.5))
Failed to evaluate expression.
- Expression: d(mod1.ec.normE,mod1.Vy)
Thanks,
Gita
Would you please help me out? I’m working with COMSOL v4a. I want to define a global constraint for electric field norm (ec.norm) using point integration and Global equation under ge model with non-zero initial condition. But I have this error:
Attempt to evaluate negative power of zero.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.ec.normE@VDN$mod1.Vy
- Defined as: (((-conj(mod1.ec.Ey))+(-conj(mod1.ec.Ey)))*((((realdot(mod1.ec.Ex,mod1.ec.Ex)+realdot(mod1.ec.Ey,mod1.ec.Ey))+realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5)*0.5))
Failed to evaluate expression.
- Expression: d(mod1.ec.normE,mod1.Vy)
Thanks,
Gita
1 Reply Last Post Jan 4, 2011, 4:03 a.m. EST
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Posted:
1 decade ago
Hi
if you look at the formula:
((((realdot(mod1.ec.Ex,mod1.ec.Ex)+realdot(mod1.ec.Ey,mod1.ec.Ey))+realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5)*0.5)
realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5
then if Ex=Ey=Ez =0 this ^-0.5 gives a NaN hence the error
two ways out:
a) either you adapt Ex,Ey,Ez to avoid Ex=Ey=Ez=0, or
b) you cheat a little (might not work) and you add in the formula (under equations)
... realdot(mod1.ec.Ez,mod1.ec.Ez)+eps)^-0.5)...
But most probably you shouldavoid "nofield" by a better BC or initial value conditions
--
Good luck
Ivar
if you look at the formula:
((((realdot(mod1.ec.Ex,mod1.ec.Ex)+realdot(mod1.ec.Ey,mod1.ec.Ey))+realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5)*0.5)
realdot(mod1.ec.Ez,mod1.ec.Ez))^-0.5
then if Ex=Ey=Ez =0 this ^-0.5 gives a NaN hence the error
two ways out:
a) either you adapt Ex,Ey,Ez to avoid Ex=Ey=Ez=0, or
b) you cheat a little (might not work) and you add in the formula (under equations)
... realdot(mod1.ec.Ez,mod1.ec.Ez)+eps)^-0.5)...
But most probably you shouldavoid "nofield" by a better BC or initial value conditions
--
Good luck
Ivar